JPH034288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming several protrusions (hereinafter referred to as dowels) on the end surface of a material by closed cold forging. In order to minimize the amount of burrs generated in order to promote the flow of the material that is effective for unloading, and to create burrs in a shape that is convenient for post-processing, a sealed mold is used at the same time as the dowel protrusion molding. This relates to constraining and generating a small amount of burr in the punch forward direction and punch backward direction within the punch.

There has been a strict demand for reducing product prices for products W3 and W4 with dowels 2 as shown in Figs. 1 and 2, and in order to meet this demand, the applicant has proposed the , has previously applied for a method of protruding the dowel 2 forward by allowing the annular protrusion 3 (ie, burr) to grow freely at the rear.

This application: Japanese Patent Application No. 120942 (1983)
The doweling method according to No. 44439) has no problems in terms of molding accuracy and mold life, but in order to allow the annular protrusion 3 to grow freely, there is still some room for improvement in material yield and removal of the annular protrusion. Ta.

In particular, the tip of the annular protrusion 3 has a wavy shape on the circumference, which obstructs automated cutting and removal of the annular protrusion 3 (burrs), and requires an independent machining process to remove the burr and allocate high process costs. It didn't happen.

However, if we try to stop the free growth of the burr and suppress the material yield and the amount of protrusion of the annular protrusion,
(In other words, if you try to do closed forging), the flow of the material will deteriorate during forming by cold forging, and according to the method described above, the material could be formed with a forming load of 240 tons, but if the free growth of burrs is suppressed, the dowels will be 80% smaller with a forming load of 300 tons. Therefore, when the molding load is further increased, the pressure load on the punch 10 and the knockout 16 increases, causing them to break, resulting in an extremely shortened mold life.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a doweling method using closed cold forging that overcomes the above-mentioned problems, in order to improve material yield and reduce the price of doweled products by facilitating burr removal.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 5 shows an intermediate product W2 with dowels 2 formed by closed cold forging. FIGS. 6 to 8 show step-by-step the doweling process by closed cold forging.

In FIG. 6, the lower mold 24 consists of a clamping ring 37, dies 25 and 26 fixed on the same axis as the punch 20, and a pressure plate 38, and a machine stand plate of the forging device (Fig. (not shown).

The dies 25 and 26 have a die-cutting space 27 that opens upward in the center, and several recessed holes 29 for forming dowels are formed downward at the bottom of the die-cutting space 27. In this embodiment, the recessed hole 29 for dowel molding is
are formed at three locations at equal pitches on a circumference concentric with the engraving space 27.

The bottom of the recessed hole 29 communicates with a relief hole 30 via a chamfered portion, and further communicates with an air vent hole 31 located below.

Furthermore, the die-cutting space 27 is formed so that its axial length is sufficiently longer than the axial length of the material W1, as shown in FIG. ing.

A die 26 is placed at the center of the bottom of this die-carving space 27.
A knockout hole 35 is formed through the hole, and a knockout pin 33 is inserted into the hole so as to be able to move up and down as the knockout 32 moves up and down.

The upper end of the knock-out hole 35 is formed concentrically with the hole 33 portion below it and has a slightly larger diameter than the hole 35 portion below it, and in this case, the knock-out hole 35 is located lower than the bottom of the die-carving space. In cooperation with the tip end surface 34 of the pin, a balance space 36 is formed that opens only at the bottom of the die-carving space 27.

The equilibrium space 36 at the upper end of the knock-out hole 35 is filled with a part of the material as a burr as the punch 20 moves forward during molding of the material W1, so that the equilibrium space 36 is located at an intermediate position between each dowel 2 and the material flow is prevented. A balancing protrusion 5 shown in FIGS. 7 and 8 protrudes from the center of the front of the material in the forward direction of the punch, which is one of the causes of increased forming resistance and promotes the flow of the material, as well as absorbing part of the pressure load. The load applied to the knockout pin 33 is alleviated by being supported by the portion constituting the outer bottom surface of the balance space 36.

On the other hand, the punch 20 is connected to a ram (not shown) of a forging device and is mounted on a lower mold 24 so that its tip end faces face each other and move back and forth.

The punch 20 is formed to have a diameter substantially equal to the inner diameter of the die-cutting space 27, and when inserted into the die-cutting space 27, it almost seals the die-cutting space 27, and also closes the outer periphery of the punch and the opposing die. carving space 2
No gap is formed between the inner circumferential wall surface 28 of No. 7 and the inner circumferential wall surface 28 of No. 7 to actively allow the escape of surplus material.

The tip surface of the punch 20 has a protruding central convex portion 21 in the center that occupies most of the tip surface, and an outer circumferential shoulder surface 23 formed on the outer peripheral side of the central convex portion 21 and slightly lower than the central convex portion 21. It consists of

Therefore, when the central convex portion 21 of the punch 20 comes into contact with the end face of the workpiece W1 in the punch retreat direction in the die-scabbing space 27, a thin annular shape is formed between the end face of the workpiece and the outer peripheral wall surface 23 on the outer peripheral side of the opposing punch tip. form a flat space.

This thin annular flat space is filled with part of the material as burrs as the punch 20 moves forward during molding of the material W1, thereby promoting flow of the material.

In addition, by forming the outer peripheral shoulder surface 23 of the punch in a planar shape substantially perpendicular to the punch axis, it is possible to suppress the occurrence of burrs larger than the pre-planned volume, and especially in the punch outer periphery and the engraving space opposite thereto. It has the function of stopping the flow of material that attempts to flow into the gap between it and the peripheral wall surface 28.

Therefore, the shape of the tip end surface of the punch 20 is similar to that of the central convex portion 21, except for the outer circumferential shoulder surface 23 formed by a slight annular flat surface substantially perpendicular to the punch axis on the outer circumferential side. The outer circumferential surface 22 of the convex portion connecting with the outer circumferential shoulder surface 23 is not only tapered as shown in the drawings of the embodiment, but also has a convex spherical shape continuous from the central convex portion 21 or a cylinder perpendicular to the outer circumferential shoulder surface 23. It may be formed by a planar shape or the like.

However, as shown in FIGS. 5 and 7, the thin annular flat space determined by the shape of the tip end surface of the punch 20 remains the same as the thin annular flat protrusion 9 on the intermediate product W2 after forging. It appears as a shape.

Therefore, in determining the shape of the punch tip, it is important to change the intermediate product W2 to the semi-finished product W3 shown in Figure 3.
When cutting the thin annular flat protrusion 9, instead of providing a separate process for removing the flat protrusion 9, the flat protrusion 9 is
The purpose is to determine the shape of the tip of the punch 20 so that a thin protrusion is formed to enable such processing.

Next, cold doweling using the closed mold described above will be explained step by step.

First, as shown in FIG. 6, the material W1 is inserted into the engraving space 27 of the lower mold 24. At this time, mold engraving space 2
7 accommodates the material W1 on its lower side, and forms a remaining cylindrical space having an appropriate axial length on its upper side.

Subsequently, as shown in FIG. 7, the punch 20 enters the die-scabbing space 27 from above, and the tip end face of the punch is struck against the end face of the workpiece W1, thereby sealing the workpiece W1 within the mold.

As a result, the dowel 2 is formed to protrude into the concave hole 29 for dowel forming, and at the same time, the counterbalancing projection 5 is constrained and generated in the balanced space 36 at the upper end of the knockout hole 35, and the flat projection 5 is formed in the thin annular flat space at the tip of the punch. 9 is generated.

In this way, in the closed type for dowel removal, by creating a slight burr, or a balancing protrusion 5, in the restraining space in the forward direction of the punch, the volume of the burr, or flat protrusion 9, produced in the backward direction of the punch can be significantly reduced. Moreover, even if the flat protrusions 9 are generated in a constrained space of a shape convenient for processing after being set in advance, the flow of the material is promoted so as to effectively effect dowel removal.

Therefore, there is little increase in forming load due to changing to closed forging, and cold doweling can be carried out easily using a closed die.

Therefore, the pressure load of the punch 20 and the knockout pin 33 as well as the dies 25 and 26 does not increase, and the lifespan of these components is increased to the same level as that of the prior art.

Next, as shown in FIG. 8, the punch 20 is raised, and then the knockout 32 is raised to knock out the intermediate product W2.

Thereafter, this intermediate product W2 is subjected to a suitable cutting process to be finished into a desired product as shown in FIGS. 1 and 2. Note that the thin annular flat protrusion 9 of the intermediate product W2 can be removed at the time of cutting and finishing the end face of the rear surface 7 in the extrusion direction as described above, so there is no need to set up an independent process for removal. .

As a result, the intermediate product W2 shown in Fig. 5 can be made by reducing the weight of the material used to form it by about 10% compared to that shown in Fig. 4. Since a separate step of cutting and removing the annular protrusion is no longer necessary, the production cost of products with dowels can be reduced.

As described above, according to the present invention, a small amount of burr is constrained and generated in the forward direction of the punch and the backward direction of the punch in the closed mold at the same time as the dowel is ejected, so that the material flow effectively acts on the dowel ejection. In addition to minimizing the amount of burrs generated to promote the process, the burrs can be set in advance and then generated into a shape convenient for processing, resulting in cold forging using a closed mold with a material yield of approximately 10% compared to conventional methods. In addition, it is easier to remove burrs in post-processing, and there is less increase in forming load due to the change to closed forging, so products with dowels can be manufactured easily.

[Brief explanation of the drawing]

FIGS. 1 and 2 are perspective views of a semi-finished product with dowels and a finished product made from a forged intermediate material. FIG. 3 is an explanatory diagram of a conventional cold forging method. Fourth
The figure is a perspective view of the forged product. FIG. 5 is a perspective view of an intermediate material formed by closed cold forging according to the present invention. FIG. 6 to FIG. 8 represent an embodiment of the present invention, and are explanatory diagrams of the doweling process. (Explanation of symbols), W1...Material. W2...Intermediate material. 2... Dowel. 5...Balancing protrusion. 9...
Oblate process. 20...Ponchi. 23...Outer shoulder surface.
24...lower mold. 27...Mold engraving space. 29...Concave hole. 34...Knockout tip surface. 35... Knockout hole. 36... Equilibrium space.

Claims (1)

[Claims] 1. Insert the material W1 of a predetermined length, the outer diameter of which is approximately equal to the inner diameter of the die-sinking space 27 of the lower die 24, into the die-sinking space 27 of the lower die 24, whose length in the axial direction is sufficiently larger than the length of the material. Then, a punch 20 whose outer diameter is approximately equal to the inner diameter of the die-scoring space 27 is inserted into the die-scoring space 27 of the lower die 24 to seal the material W1 in the die-scoring space 27,
In a dowel extraction method using closed cold forging, in which the punch 20 is pressed against the material W1 to protrude the dowel 2 into several recessed holes 29 for dowel forming formed at the bottom of the die-scabbing space 27. , At the same time as the dowel 2 is protruded and molded, the knock-out tip surface 34 is positioned slightly lower than the bottom surface of the die-scabbing space 27 at the upper end of the knock-out hole 35 passing through the lower die 24 as a burr due to surplus material. The punch 20 constrains and generates the balancing protrusion 5 in the space 36 and faces the lower die 24.
A method for doweling by closed cold forging, characterized in that a thin annular flattened projection 9 is constrained and generated in a portion formed slightly lower than the center portion on the outer periphery side of the tip surface of the dowel.